In order to gain widespread acceptance, new technology in biomedical research fields typically should address current unmet experimental needs, and should be relatively easy to integrate into standard research lab protocol. Many advances require researchers to discard well accepted protocols and in favor of more complex devices, methods, or materials. For example, the hesitancy of researchers to adopt unfamiliar and potentially more complex protocols has stymied broad dissemination of Bio-MicroElectroMechanical Systems (bioMEMS). Researchers also are hesitant to use and fabricate complex bioMEMS devices in highly variable biological systems when the possible gains seem marginal at best. In order for the field of bioMEMS to mature beyond proof-of-concept demonstrations, researchers may soon focus on developing systems using microscale phenomena, and may work to integrate these phenomena into standard laboratory methods.
The primary methods for oxygen variation in standard cell biology experimental protocols typically involve either changing the global incubator oxygen concentration or using modular hypoxic chambers. Modular hypoxic chambers offer a simple approach to compartmentalize standard incubators into several oxygen concentrations. However, the size of these chambers limits the number of hypoxic chambers (and consequently conditions) to three to four for each incubator, and reduces the remaining available incubator space for other investigations. Because incubators are large and expensive, limiting the available incubator space to accommodate only ten multiwell plates is far from ideal. These issues are especially important when working with highly variable primary mammalian cells because performing all experiments on the same batch of cells reduces inherent animal to animal variability.
Realizing these limitations, several groups have developed devices to control the oxygen environment around adherent cell cultures (Tilles, et al. Biotechnology and Bioengineering 73(5): 379-389 (2001); Allen et al., Biotechnology and Bioengineering 82(3): 253-262 (2003); Vollmer, et al., Lab on a Chip 5(10): 1059-1066 (2005); Lee, et al. Lab on a Chip 6(9): 1229-1235 (2006); Mehta, et al., Biomedical Microdevices 9(2): 123-134 (2007)). However, these devices are specialized for their unique application and require complex fluidic handling and controls to maintain the cells under perfusion, which impedes widespread adoption of these techniques. Other demonstrations of oxygen control in microfluidic channels used electrolysis to generate oxygen (Vollmer, et al., Lab on a Chip 5(10): 1059-1066 (2005)), which further complicates device fabrication and operation. Thus, a need exists for improved devices and methods for controlling gas (e.g., oxygen) concentrations within a multiwell plate.